Methodology

Standard, documented formulas

Every calculator uses an established formula, not a guess. Loan and mortgage payments use the standard amortization formula; compound interest uses the recognised future-value equations; BMI follows the WHO definition; calorie needs use the Mifflin-St Jeor equation; income tax applies the published bracket tables. Where a calculator relies on a specific source, that source is cited on the page.

Pure, tested calculation code

The maths is separated from the interface. Each formula is written as a pure function — given the same inputs it always returns the same output — and covered by an automated test suite. This keeps the underlying calculation correct and independent of how the result is displayed.

Honest assumptions

Real-world figures depend on details a calculator cannot know, so every calculator states its assumptions plainly. The mortgage calculator shows the full PITI payment, not just principal and interest. The savings calculator lets you choose the compounding frequency rather than hiding one. The auto loan calculator lets you decide whether tax and fees are financed. We would rather show an honest assumption you can change than a tidy number that quietly misleads.

The limits of an estimate

A calculator produces an estimate from the inputs you give it. It cannot account for your full circumstances — local rules, fees, credit terms, or personal factors. Treat every result as a well-founded starting point, and consult a qualified professional before an important decision. See our Terms of Use.

Kept current

Figures that change over time — tax brackets, standard deductions, contribution limits — are reviewed and updated when the authorities publish new values. Calculators that depend on a dated figure indicate the year the data applies to.

Found a problem?

If a result looks wrong, tell us — accuracy is the whole point of the site. See the Contact page.